package demo1;

import java.util.List;

public class MyLinkedList {
    //静态内部类
    static class ListNode{
        public int val;
        public ListNode prev;//前驱
        public ListNode next;//后继

        //构造方法
        public ListNode (int val){
            this.val = val;
        }
    }

    public ListNode head = null;//标记头
    public ListNode last = null;//标记尾巴

    //展示
    public void display(){
        ListNode cur = head;
        while(cur != null){
            System.out.println(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else {
            node.next = head;//把node得后继接上
            head.prev = node;//把head的前驱接上
            head = node;//移动head
        }

    }

    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        } else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    //任意位置插入，第一个数据为0号下标
    public void addIndex(int index, int data){
        if(index < 0 || index > size()){
            System.out.println("index不合法");
            return;
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == size()){
            addLast(data);
            return;
        }
        ListNode cur = searchIndex(index);
        ListNode node = new ListNode(data);
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }
    //找到index的下标
    public ListNode searchIndex(int index){
        ListNode cur = head;
        while(index != 0){
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contain(int key){
        if(head == null){
            return false;
        }
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        if(head == null){
            return;
        }
        ListNode cur = head;
        while(cur != null){
            if (cur.val == key){
                if (cur == head){
                    head = head.next;
                    if (head != null){
                        head.prev = null;
                    }
                } else{
                    cur.prev.next = cur.next;
                    if (cur.next != null){
                        cur.next.prev = cur.prev;
                    }else{
                        last = last.prev;
                    }
                }
                return;//删完走人
            }else {
                cur = cur.next;
            }
        }
    }

    public int size(){
        int cnt = 0;
        ListNode cur = head;
        while(cur != null){
             cnt++;
             cur = cur.next;
        }
        return cnt;
    }
}
